1. Field of the Invention
The present invention relates generally to Ethernet systems and, more particularly, to a hybrid technique in energy efficient Ethernet (EEE) physical layer devices (PHYs).
2. Introduction
Energy costs continue to escalate in a trend that has accelerated in recent years. Such being the case, various industries have become increasingly sensitive to the impact of those rising costs. One area that has drawn increasing scrutiny is the IT infrastructure. Many companies are now looking at their IT systems' power usage to determine whether the energy costs can be reduced. For this reason, an industry focus on energy efficient networks has arisen to address the rising costs of IT equipment usage as a whole (i.e., PCs, displays, printers, servers, network equipment, etc.).
In designing an energy efficient solution, one of the considerations is the traffic profile on the network link. For example, many network links are typically in an idle state between sporadic bursts of data, while in other network links, there can be regular or intermittent low-bandwidth traffic, with bursts of high-bandwidth traffic. An additional consideration for an energy efficient solution is the extent to which the traffic is sensitive to buffering and latency. For example, some traffic patterns (e.g., HPC cluster or high-end 24-hr data center) are very sensitive to latency such that buffering would be problematic. For these and other reasons, applying energy efficient concepts to different traffic profiles would lead to different solutions. These varied solutions can therefore seek to adapt the link, link rate, and layers above the link to an optimal solution based on various energy costs and impact on traffic, which itself is dependent on the application.
One solution to addressing low link utilization is to reduce the high data capacity when it is not needed, thereby saving energy. In other words, a link can use a high data rate when data transmission needs are high, and use a low data rate when data transmission needs are low. In another solution, the link can be designed to enter into a low power idle (LPI) mode where the bulk of the PHY and the energy on the link is turned off (put to sleep) when there is no data transmission. When data is transmitted, it is transmitted at full PHY capacity. While this low power idle mode can save the most power, it does present some challenges that make it unsuitable for a class of solutions that may have specific requirements such as low latency. What is needed therefore is a flexible and efficient link utilization mechanism.